Turning sunlight into electricity is big business, with the market for photovoltaic technologies expected to grow a whopping 39.9% over the next five years, according to Georgina Benedetti, an energy analyst for Frost & Sullivan.

“Solar is predictable,” says Robert Wendt, a chief technology officer for solar company XsunX. “It’s adaptable. It’s compatible with other renewable sources such as wind. It allows installers to provide performance guarantees; it requires little maintenance; and it has no negative impact on the environment.” And soon, solar may be cheap enough to compete with traditional power. Third-generation solar will “provide electricity on a massive scale, using low-cost raw materials,” predicts Stephen Squires, CEO of solar cell manufacturer Solterra Renewable Technologies, Inc. “A third-generation solar power plant will produce more megawatts per day than first- or second-generation solar plants can produce in a month,” he says.

First-generation solar cells, accounting for the lion’s share of today’s market, are mostly silicon-based, while second-generation refers to “thin films’ made bylayering plastic or glass withphotovoltaic material such as copper indium gallium selenide (CIGS).High-efficiency third-generation mat-erials include polymers and plastics; molecule-sized semiconductor particles called quantum dots and biomimetic, or “life-imitating” dyes. All can convert more than silicon-based cells’ 31% of solar power to electricity.

Dye-sensitized solar cells (DSC) mimic photosynthesis, says LivinGreen Materials CEO Chris Tagge, Ph.D., a polymer chemist. The cells work well in artificial light and reduced sunlight and “the energy payback time of DSC is the shortest among all solar technologies,” he says. Thebattle between third-generation quantum dots and second-generation CIGS is heating up. Nano-sized quantum dots have “a theoretical energy conversion efficiency potential nearly double that of all other solar technologies,” says Squires, whose company makes them. CIGS, he says, are outdated, because they depend on rare earth metals. Wendt disagrees. His firm, XsunX, plans to use the same hard-drive manufacturing techniques that brought computers to the masses. “Our approach to CIGS can be compared with Ford’s approach to cars,” Wendt says. “While Henry Ford did not invent the car, he did revolutionize how cars are built through manufacturing innovations and engineering improvements.” Siding with CIGS, Vignesh Gowrishankar, a solar energy expert with the National Resources Defense Council, says, “quantum dots…may have strong theoretical potential, but getting an electrical current out of a quantum dot array may prove practically challenging, especially outside the lab.”